The present invention relates to a contact system for a short-circuiting device for a switchboard.
Electrical switchboards for voltages in the range from 1 to 52 kV, which range is generally described as the medium-voltage range, are designed in the form of metal-encapsulated gas-insulated switchboards, see DE 43 02 416, in which load isolating switches, grounding switches and fuses are accommodated as functional units.
When an arcing fault occurs in a switchboard of this kind, the effects of the arcing fault must be kept to a minimum. If the combustion time of such an arcing fault is appropriately long, the pressure and temperature within the switchboard can increase to such an extent that the metal encapsulation can burst or melt; in order that persons are not injured or even killed as a result of an uncontrolled outflow of heated gas into the room in which the switchboard is located, with many switchboards so-called designated breaking points are provided in the housing encapsulation through which, in the event of their breakage, the heated gas flows out in a controlled manner in a certain defined direction so that any operating personnel who may be in the room are not injured. A switchboard is described, see also DE 31 31 417, in which a short-circuiting device is provided, which on the occurrence of an arcing fault short circuits the phases or connects them to ground so that the short circuit is diverted as soon as it occurs and the effects of the arcing fault on the interior of the switchboard are limited. For this purpose, this switchboard has a pressure sensor, which by means of a storage spring gearbox brings moving switching contact pieces, which are designed in the form of contact blades, into contact with fixed contact pieces situated on the phase conductors, the drive being designed as a spring drive; the pressure sensor acts on a latching point, which releases the drive spring and thus drives the moving contact pieces into the fixed contact pieces at high speed, as a result of which the phases are short-circuited thus suppressing the arc.
With this switchboard, the fixed contact pieces are exposed within the switchboard so that certain distances have to be maintained between the fixed contact pieces and the grounded encapsulation.
As a basic principle, there is a requirement to make switchboards of this type as compact as possible, as the available space is limited and therefore expensive.